A fleet of self-driving
Ubers in Pittsburgh.Business
Insider/Corey Protin

Self-driving cars might make your future commute a lot more
pleasant, but they won’t eliminate traffic.

Execs like Google cofounder Sergey Brin
have touted traffic reduction as one of the many
benefits of having self-driving cars on the road. The idea
is that autonomous cars will eliminate accidents caused by human
error, a major contributor to traffic.

But experts say the vehicles’ impact on traffic will either be
minimal or negative.

Lew Fulton, a co-director at UC Davis’ Institute of
Transportation Studies (ITP), told Business Insider that
autonomous vehicles won’t fix congestion woes unless a pricing
system is put in place that discourages zero-occupancy vehicles.

“We are especially concerned about zero-occupant vehicles that
can happen with automated vehicles,” Fulton said. “That scenario
is especially plausible with private ownership of those vehicles
and no limits to what we can do with them.”

For example, many companies are
interested in programming autonomous cars to run errands or
pick-up packages, but these efforts could increase traffic by
multiplying the number of zero-occupant cars, or “zombie cars,”
on the road, Fulton said.

Congestion could also worsen as companies like Lucid Motors
explore designing self-driving vehicles around comfort,
like installing reclining seats.

Consumers may opt to live farther outside of cities if they
can commute in vehicles that allow them to sleep and relax. But
that sprawl increases the number of people traveling in and
out of cities during rush hour, Fulton said.

Self-driving cars can still contribute to congestion even if
they operate as part of a ride-hailing network, like Uber.

Without the cost of a driver, Fulton said he worries self-driving
Ubers or Lyfts will become so cheap there will be no financial
incentive to opt for car-sharing services like UberPOOL.

“I think it’s going to take some kind of pricing system that
discourages zero-occupant vehicles and also makes penalties for
single-occupancy vehicles,” he said.

Fulton isn’t alone in this line of thinking.

Matthew Turner, an economist at Brown University, has studied
road congestion and co-authored a 2011 paper titled “The
Fundamental Law of Road Congestion.” Turner found that vehicle
pricing structures have had the biggest effect on reducing travel
time, more so than increasing public transit access.

“Maybe autonomous cars will be different from other capacity
expansions, but of the things we have observed so far, the only
thing that really drives down travel times is pricing,” Turner
told the New York Times.

Some cities have already mobilized to discourage people from
taking cars alone. States like California and
Colorado have installed high-occupancy toll lanes that
single-occupancy must pay a fee to use. That fee increases
during rush hour.

“We have to figure out systems that promote pairing,” Fulton
said. “It really is a silver bullet if we can do it.”